Beverage dispensers are used at many locations to provide consumers with beverages, such as fruit juices, that are a mixture of previously stored concentrate and fluid such as water. Many beverage dispensers have a space for storing the concentrate and a plumbing system which includes an inlet coupling through which fluid from an external source is supplied. A proportion pump is used to force the concentrate and water separately to a dispensing nozzle where it is mixed immediately prior to being discharged into a cup or other container. Ofter, a double-acting piston pump is used to force the concentrate and water to the discharge nozzle. The pump is set to deliver the mixture at a set ratio, for example between 4:1 and 5:1 parts water to concentrate.
An important consideration when providing beverages is preventing the growth of fungus and bacteria, which can contaminate the end product and be a source of gastric distress. Most beverage concentrates are provided with sodium benzoate and other preservatives in order to inhibit the growth of fungus and bacteria. However, once the beverage concentrate and water is mixed, the preservatives are diluted to the point where they are no longer effective for inhibiting the growth of fungus and bacteria. Fungus and bacteria frequently develop within the beverage dispenser plumbing downstream from the point where product concentrate and water are mixed. One means of minimizing the growth of fungus and bacteria in beverage dispensers is to have separate product concentrate and water lines that are not joined until they reach the dispenser nozzle.
The requirement that concentrate and water be kept separate prior to discharge has made it difficult to provide beverage dispensers capable of delivering two or more different types of beverages. One disadvantage of the prior systems is that they are unable to consistently deliver the exact amount of water needed to properly dilute the concentrate. Consequently, these systems produce beverages of uneven, and sometimes unacceptable, quality. Moreover, these systems typically employ either electrically or gas (CO2) driven pumps. Providing beverage dispensers with these pumps adds to both the cost and complexity of their operation.